Process of extracting metals.



No. 788,912. PATENTED MAY 2, 1905.

' V J. A. JUST.

PROCESS OF EXTRAGTING METALS.

APPLICATION FILED OUT- 7. 1904.

IIILVESSES; '5 r f B) Will M ATTORNEY.

Patented May 2, 1305.

UNITED STATES PATENT OFFICE.)

JOHN A. JUST. OF PULASKl, .NEVV YORK, ASSIGNOR TO JUST MINING & ,XTRACTION 00., OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

PROCESS OF EXTRACTING METALS.

srncrmca'rrox formingpart of Letters Patent No. 788,912,. dated ma 2, 1905. 1

Application filed Ottcber '7, 1904. Serial No. 227,523.

To all whrnn it may concern.-

Be it known that 1, JOHN A. JUsr, a citizen of the United States, and a resident of Pulaski, Oswego county,'State of New York, have invented certain ncw and useful improvements n Processes of Extracting Metals. of which the following is a specification, accompanied by a drawing.

This invention relates to processes of extracting metals from their ores, more particularly to the extraction of gold and silver from oxidized and unoxidized ores.

The objects of the invention are to extract all the precious metals in the ore, as gold and sil er, more quickly and economically than he: ctofore; and the invention consists of a new process of extraction, substantially as herein after fu ly described and claimed in this specili cation and as illustrated by the suitable apparatus in the accompanying drawing, in which the figure is a side elevation of suitable apparatus for carrying out the process.

In treating unoxidized sullid ores containing gold and silver the ore is first roasted, and in carrying out the roasting process the ore should preferably be crushed until it will pass through a. sieve of suitablemesh-as, for instance, a sixty-mesh sieve, which has been if defound of suitable size for extraction. sired, asomewhat coarser or a liner sieve may be used, according to the apparatus available for circulating the extracting liquid.

In ore that contains approximately ten ounces of gold per ton and two per cent. of silver about live per cent. of sodium chlorid in solution is added to the, ore to moisten the ore, and the ore and solution are thoroughly mixed in anysuitahle manner in order to uniformly distri buto the salt throughout the mass, which is then dried, thereby driving off the water and insuring the uniform distribution of the salt throughout all the particles of themass of ore. Vi'ith ores having dill'ercnt percentages of gold and silver asuitablc percentage of sodium chlorid in solution should be added, and, if desired, calcium chlorid in solution instead of sodium chlorid may he used. The mass of ore is then calcined at alow red heatuntll the check test shows that the sullids are decomposed, which has been found to take from one to one and a half hours. The check test maybe made by taking a small quantity from the roast, washing out the water-soluble chloride with water, adding strong nitric acid to dissolve any undccomposed sullids if still present, then filtering and testing the filtrate with hydrochloric acid. If the sulfids are decomposed into chlorids, hydrochloric acid will not give a precipitate in this solution; but if the sullids are still present nitric acid will decompose them and form silver nitrate, which on the addition of hydrohcloric acid will precipitate silver chlorid. When this check test shows the absence of sullids, the roast is complete, and the ores are ready for further treatment. In the check test strong nitric acid-is preferably used, since silver sullld is soluble therein and silver chlorid is not soluble therein. lVh en the process of chloridizing is complete, the ores are transferred to a suitable vessel, which maybe termed the extraction vessel, (indicated by A in the drawing.) The mass is first washed with water, which may he led to the vessel A from the water-pipe B, and the washing is continued until substantially all of the soluble salts present are extracted. The vessel A is provided with an outletpipe C, having a controlling-cock l), which in this instance is a two-way cock controlling the pipe O, and a branch pipe E, emptying into a suitable tank F. The pipe E, as shown. is provided with a cock 7, and another branch pipe, ll, having a cock 1., leads to the linal washing-tank J. In the preliminary washing of the ore the cock D is turned to close the outlet of pipe 0 and open the pipe E, and the cock (,1 also opens pipe E to the tank F, so that the water entering from the supply-pipe B passes through the tank A, out through pipes C and E to the tank F. The ore is washed until no reaction is obtained on adding potassium t'errocyanid or other suitable reagent, indicating the absence ot'coppcr, zinc, and other metals, and no precipitate is obtalned on adding calcium chlorid, indicating the practical absence of sulfates.

Suitable means are provided for admitting chlorin to the tank A, asby means of the l ing to the conditions of extractionas, ford chlorin-pipe K, provided with the cock L and leading to the bottom of the tank, as shown.

Preferably in the bottom of the tank is ar- V a suitable medium.

ranged a strainer O, and the pipe 0 communicates with the tank A, preferably below the strainer.

In carrying out my improved process the chloridized ore is chlorinated, and one of the features of my invention consists in chlorinating the chloridized ore in the presence of a medium which is chemically inert to the metals themselves to be extracted, but is capable of dissolving the salts of the said metals. The medium in the presenceof which chlorination is carried out is capable of taking up silver chlorid in solution, thus extracting the silver chlorid while the gold is chlorinating, and it also takes up auric chlorid in solution as it is formed in. the process of chlorination. I havefound that calcium-chlorid solution is Calcium-chlorid solution is capable of holding the chlorin and oftaking up and dissolving auric chlorid and silver chlorid. After the washing has been completed calcium-chlorid solution, acidified with hydrochloric acid and of specific gravity about 1.40, containing about forty-one per cent. of calcium chlorid, is added to the ore in the proportion of between two and a half to three times the weight of the ore. The heavy syrupy calcium-chlorid solution is acidified in order to make it thinner, and thus facilitate filtration. By acidifying the solution its property of dissolving silver chlorid is still further increased. Sufficient calcium-chlorid solution should be added to the ore to provide a layer of solution over the ore of from one-third to one-fourth the depth of the ore. In the process of chlorination the addition of the calcium-chlorid solution saves the chlorin and facilitates the extraction, because the calcium chlorid absorbs the chlorin,

and the density of the solution restrains the chlorin from escaping, thereby keeping the chlorin in direct contact with the ore. The chiorin gas diffuses readily, and the gold-ehlorid solution as fast as it is formed also diffuses -readily throughout the calcium-chlorid solution. The calcium-chlorid solution is also at the same time dissolving the silver chlorid. After the addition of the calcium-chlorid sol ution as described chlorin gas is passed into the tank through the chlorimpipe K, during which operation the valve I) is turned to close the pipe 0 and cut off the extractor A from the remainder of the apparatus. The chlorin gas is passed in or into the extractor for several hours or until the mass is saturated and the gold is all in solution, the time depending upon the quantity of gas passing and the amount of gold contained in the ore. When .the solution in the extractor A is saturated with chlorin, it may be allowed to stand, or the solution maybe filtered directly, accordinstance, the fineness of the ore. During chlorination the ore is preferably kept agitated, and any suitable well-known means may be provided for agitating the ore in the extractor.

The gold may also be chlorinated by the use of a hypochlorite, preferably calcium hypochlorite or bleaching-powder. The bleaching-powder is incorporated with the roasted and washed ore in the extractor A while still moist, and sufficient water, preferably acidified with hydrochloric acid. is added to combine with the lime base of the calcium hypochlorite, thereby producingnascent chlorin, which acts as a powerful solvent for gold. In the place of the acidified water acidified caicium-chlorid solution may be added, as hereinhefore described. In the reaction calcium chlorid is formed and chlorin is liberated, the stock of cal ium chlorid being thus kept up, which more than makes up for any mechanical losses in it which may occur. The excessive calcium chlorid may be used afterward in roasting for chloridizing the ore, especially in mining districts where salt is scarce. The chlorination in a case where hypochlorite is used is allowed to continue for from three to five hours, more or less, according to the quantity of the gold in the roast to be dissolved and taken up in solution.

After chlorination the ore is leached with calcium-chlorid solution of the same strength already described until the leachings as they come from the ore show no milkiness on diluting a small sample with from five to ten times as much water and shaking, the milkiness showing the presence of the silver chlorid and clearness the absence of the same. The gold will be extracted long before the silver, and when the dilution test referred to shows the absence of silver chlorid the silver and gold available have all been extracted. During the step of leaching the valves G and I are closed and the two-way cock I) is opened to afford communication between the extractor A and the receiving-tank P. The small samples for testing may be taken from the end of the pipe 0 or from any other suitable placeas, for instance, at the small cock Q near the tank A.

After leaching the cock D is turned the pipe C and open pipe E and the valve I is opened. The mass of ore in the extractor A is then washed with a little water, which may be hot, to recover the calcium chlorid remaining in the mass, which is recovered:in the well J asa weak solution of calcium chlorid, whichmay be used afterward in the roast- IIO to close ing process for chloridizing, it being of suitare in the form of their chlorids in acalcium-' chlorid solution, which solution should be maintained in an acid state, the acidity being 3 imparted by hydrochloric acid in a-limited quantity only. The solution should be rendered decidedly acid to blue litmus-paper.

In carrying out the process a precipitatingtank R is preferably provided, connected to the receiving tank or vat P by the pipe S, provided with the cock T, and after the solution of silver and gold chlorids has been obtained in the vat P it is transferred into the precipitating-tank R. Preferably the precipitat-ing-tank R is provided with means for stirring the contents of the tank, in this instance with an air-pipe U, provided with suitable apertures. The use of air for stirring the contents of the precipitating-tank has the advantage that after the complete precipitation the air rids the solution of its retained hydrogen gas, and the iron being present in a ferrous state will quickly oxidize in the presence of the oxygen of the air which passes through the liquid to the ferric state and becomes harmless. The metallic zinc which I add to the material in the precipitating-tank R is preferably in the form of bars, scrap, or other suitable form, and the currents of air issuing from the apertures in the pipe U will keep the zinc bars, scrap, or other forms clean. The pumping of the precipitate from the tank R is also facilitated by air, which agitates the precipitate and keeps it in suspension.

In order to release the silver chlorid from the calcium-chlorid solution, the latter solution may be somewhatdiluted with water, just sufficientfor the solution to assume a slight cloudinessormilkiness. Thisstep,whilenota r. 'tcessary one in the carrying out of the process, is preferable, because it hastens the step of precipitation of the metals which follows. A suitable substance or metal is now added to the calcium-chlorid solution which is capable of precipitating the gold and silver in the form of salts, or, preferably, directly in a metallic state. For this purpose i prefer to use a metal-as, for instance, metallic zinc'which will remove the metallic salts in thecalciumchlorid solution in a reduced state or in metallic form.

When a. filtered sample from the precipitating vat or receiver R no longer shows milkiness on dilution with water and does not show purple color on the addition of stannous chlorid pr give a colored precipitate with hydrogen fsullid, this step of the process of reduction is complete.

According to my new process it will be seen that both silver and gold are obtained at the same time or in one operation, which greatly simplifies the process and prevents losses, more especially of the gold.

As shown, A pipe V leads from the precipitating-tank E to a filter-press W, and the so lution containing the precipitate is pumped into the filter-press by means of any suitable pump X. The filter-press W may be of any suitable well known form or construction which separates the precipitate from the liquor. The liquor is drawn off from the filter-press W through the pipe Y to the-tank Z, which contains the liquid calcium chlorid recovered for future use, thereby contributing 7a chlorid, it does no harm, its quantity being small, and when it hasaccumulated sulliciently to warrant its removal and recovery it may be readily removed from the calcium-chlorid solution by treating it with an alkaline sulfid, as sodium or calcium sulfid, preferably the latter, since calcium chlorid is then formed,

thus adding to the solvent used. 1 Hydrogen sultid may also be used instead of sodium or calcium sulfid. or the zinc chlorid is preferably precipitated with calcium hydroxid as zinc hydroxid and filtered. The calcium chlorid is thus purified in a simple way and the zinc is recovered. Since the goldis precipitated by ferrorj salts, which is the only 95 salt likely to be ptesent in the calcium-chlorid solution and in small quantity at this stage, it is advisable to see that before usingthe calcium-chlorid solution for fresh extraction all ferrous salts are oxidized to ferric salts. This takes place quickly when the calcium-chlorid solution is exposed to the air-as, for instance, to the'air admitted through the pipe U or to atmospheric air. The calcium-chlorid solution containing the ferrous salts is colorless, like water; but when the ferrous salt is oxidized to ferric salt the solution has the color of commercial hydrochloric acid+that is, light greenish yellow. The hrodrogcn gas evolved by the action of hydrochloric acid on zinc reduces the ferric salt present during the treatment of zinc to the ferrous state. To effect the oxidation of the ferrous salt to ferric salt, if desired, the calcium-chlorid solution, especially in case it has become somewhat diluted in the process of extraction, may be run over shallow heated pans from one to the other, and. in this way both concentration and oxidation will be effected. v

The metallic precipitate is well washed with water until free from all soluble matter, and it is then dried and may befuseddirectly, melted, and cast into bars. These bars will contain all the silver and gold of th'core and any copper that may have been in the precipitate. 1 .f

. In case the ore to be treated is a naturally oxidized ore the crushed ore is'roasted with about two per cent. of sodium chlorid' in solution as may be found necessary, as hereinbefore described and according to the silver contained in the ore to be chloridized. The remainder of the treatment for carrying out my process of extraction of the oxidized ore is the same as already described for unoxidized ore. It has been found that low and high grade ores and oxidized and unoxidized ores may be mixed and the process hereinbefore described carried out so that all the gold and silver is recovered therefrom.

In case it is desired to refine the gold-silver-zinc precipitate obtained by the metallic zinc process the preferable method of refining is by smelting with lead after distilling off the zinc. This method is preferable to the ordinary acid methods, because most of the zinc is thus recovered at once in a form available for use as a precipitant. The dried precipitate is mixed with granulated lead in about the proportions of one to three times the weight of lead to the dried precipitate and charcoal in the proportion of about one-tenth of the weight of the lead. The mixture is placed in a graphite retort and heated, preferably, by means of a gas-furnace. The zinc begins to distil off at about 7 Fahrenheit.

and is practically all driven off in four or five hours, the temperature being finally raised to about 1,300 Fahrenheit. Very little gold or silver is thus volatilized, and whatever minute traces that do volatilize remain with the zinc, which is used for subsequent precipitation. The metallic-zinc vapors may be received in a well-cooled condenser, in which most of the zinc condenses as dust, especially while carbon monoxid is being evolved. The material in the retort at the end of the distillation is in appearance like that at the start, but on examination there will be found small shots of bullion all through it and usually several larger masses. The residue may be poured from the retort in a loose state, like sand. It should be mixed with about four or five parts of litharge and melted down on a test, a small amount of iron-filings and silica being added, if necessary. After thorough fusion the slag is skimmed off and the lead cupclled, the re,- sulting litharge' being used for the next operation. The bullion after remelting may be cast into bars, which are ready for parting.

If desired, the chlorination may be complated in a separate vessel before the calcium- 7 chlorid solution isadded. Furthermore, the

solution in the receiving-tank P may be pumped back into theextracto-r A through pipee by means of a suitable pump f during the leaching with calcium-chlorid solution,

thereby keeping up a continuous circulation until the leaching is completed.

This invention may be carried out in any suitable apparatus and in a variety of ways, and therefore I do not limit the invention to the details of the steps of the process.

My improved process may also be applied to the extraction of silver alone in case there is no gold present in the ore, in which case the step of chlorination is omitted and the chloridized ore is treated with calcium-chlorid solution to dissolve the silver chlorid.

I claim, and desire to obtain by Letters Patent, the following:

' 1. The process of extraction, consisting in extracting precious metals in the form of metallic salts, with acidified calcium-chlorid solution.

2. The process of extraction consisting in extracting precious metals in the form of metallic salts, with acidified calcium-chlorid solution of about 1.40 specific gravity.

3. The process of extracting metals'in the form of metallic salts, consisting in chlorinating chloridized ores in the presence of acidified calcium-chlorid solution of about 1.40 spe' cific gravity.

4. The process of extracting precious metals in the form of metallic salts, consisting in chlorinating chloridized ores in the presence of acidified calcium-ch10: id solution.

5. The process of extracting metals in the form of metallic salts, from sulfid ores containing gold and silver,which consists in chloridizing the ores, and adding acidified calciumchlorid solution of about 1.4) specific gravity thereto, chlorinating the mass in the presence of the ealciumchlorid solution, and leaching with an additional amount of said calciumchloz'id solution until the extraction is complete. 1

6; The process of extracting metals in the form of metallic salts, from sulfid ores containing gold and silver, which consists in chloridizing the ores, washing the same to extract all the water-soluble salts, adding acidified calcium-chlorid solution of about 1.40 specific gravity thereto, chlorinating the mass in the presence of said calcium -chlorid solution, leaching with an additional amount of said calcium-chlorid solution until the extraction is complete, precipitating the gold and silver with a suitable substance, and separating the precipitate from the solution.

7. The process of extracting silver from chloridized ores consisting in first chloridizing the ore, then treating the chloridized ore with acidified calcium-chlorid solution of about 1.40 specific gravity.

IIO

8. The process of extracting metals in the form of metallic salts, from sulfid ores containing gold and silver, which consists in chloridizing the ores, chlorinating the mass in the presence of acidified calcium-chlorid solution of about 1.40 specific gravity, and leaching I the mass in the presence of acidified calciumchlorid solution of about 1.40 specific gravity, leaching with an additional amount of said calcium-chlorid solution until the extraction is complete, precipitating the gold and silver, and separating the precipitate from the solu: tion.

10. The process of extracting precious metals from their ores, consisting in treating the chloridized ore with acidified calclum-chlorid solution, precipitating the gold and silver and separating them, and recovering the calciumchlorid solution for reuse. I

11. The process of extracting precious met tied calcium-chlorid solution, precipitating the gold and silver and separating them, and recovering the calcium -chlorid solution for reuse.

In testimony whereof I have signed this specification in the presence'of two subscribing witnesses,

c 7 JOHN A. JUST. Witnesses:

E. VAN ZANDT, H. L. OBERTENFFER.

als from their ores, consisting in chlorinating 5 the chloridized ores in the presence of acidi-. 

